#include <iostream>
using namespace std;

int main() {
	int n, m, x, y;
	cin >> n >> m >> x >> y;
	x--, y--;
	int *arr = new int[n * m];
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			arr[i * m + j] = (i % 2 == 0 ? i * m + j : i * m + m - j - 1);
		}
	}
	cout << endl << arr[x * m + y];
	return 0;
}